1. Field of the Invention
The present invention relates to an electrostatic recording head used in an electrostatic plotter or the like.
2. Description of the Related Art
A conventional electrostatic recording head has a plurality of needle electrodes arranged in an almost perpendicular direction to a direction of feeding a recording blank form and a plurality of auxiliary electrodes arranged in the vicinity of the needle electrodes. The plurality of needle electrodes are divided into a plurality of groups, and the needle electrodes in respective groups are arranged so as to oppose to two auxiliary electrodes. Then, an electrostatic latent image of one line portion is formed by performing such an action that discharge is generated by applying constant voltage (e.g., -300 V) selectively to respective needle electrodes in one group and also applying constant voltage (e.g., +300 V) to the auxiliary electrodes corresponding to the needle electrodes successively with respect to the needle electrodes of respective groups.
Now, it is generally known that variable density striations are generated parallel to the direction of feeding a recording blank form when a picture image smeared out black on the whole surface for instance is outputted in the electrostatic recording head of a multiplex system described above. Various causes such as that polarization is produced in a dielectric layer of the recording blank form by applying voltage to the auxiliary electrodes and space distribution of an electric field becomes uneven when voltage is applied again to the auxiliary electrodes before the polarization is moderated, that a large capacity is produced at an end portion of the group since the needle electrodes are arranged densely, and further that the space distribution of the electric field becomes uneven remarkably at the end portions of the groups when voltage is applied to almost all the needle electrodes included in the group may be cited for the above. Moreover, the generation of such variable density striations is also affected not a little by humidity, temperature, nature of the recording blank form or the like. There are a large number of causes of generating variable density striations as described above. Therefore, it has been an important subject how such variable density striations are to be reduced in a conventional electrostatic recording head of a multiplex system.